With the development of semiconductor low temperature polysilicon thin film transistors (LTPS TFT), and because of the ultrahigh carrier mobility characteristics of the semiconductor used in the LTPS TFT, the corresponding peripheral integrated circuits of a panel have become the focus of people's attention. A lot of manpower devote to the related technology of the system on the panel (System on Panel, SOP) research, and gradually make it become a reality. At the same time, due to the high mobility of the semiconductor elements of the LTPS TFT, its leakage characteristic becomes quite poor in comparison with the amorphous silicon (Amorphous silicon, a-si). The leakage current becomes an issue which is not negligible in the design of the LTPS TFT. Therefore, how to effectively control the leakage current of the LTPS TFT has become a problem in various panel designs.
In addition, in a general process of LTPS TFT panel design, a metal light shielding layer only has a function of shielding a back channel of a TFT device so as to reduce a photogenerated leakage current of the TFT device. Therefore, a utilization rate of the conventional metal light shielding layer is not high.